Method of producing iron core

ABSTRACT

An iron-core producing method is provided that blanks iron cores from an iron strip by guiding the iron strip sequentially through an iron core-producing apparatus having a plurality of workstations. The method includes guiding, by a guide, the iron strip to a first workstation having a punch that intrudes into caulking portion-forming holes, and simultaneously forming, by the first workstation, first plural sets of caulking portions at a predetermined pitch in the iron strip. The method also includes guiding the iron strip from the first workstation to a second workstation within the iron-core producing apparatus, and forming, by the second workstation, a first iron core from the iron strip by blanking, such that tooth portions of the first iron core are disposed at lower sides of respective yoke portions.

This application is a continuation of pending U.S. patent applicationSer. No. 11/786,810, filed Apr. 13, 2007, which is a division ofabandoned U.S. patent application Ser. No. 10/960,659, filed Oct. 7,2004, which claims priority to Japanese Application No. 2003-352313,filed Oct. 10, 2003. The entire disclosures of the above-identifiedapplications, including the specifications, drawings and claims areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

This invention relates to a method of and an apparatus for producing aniron core.

An iron core for a motor is formed from a strip by blanking. This ironcore is usually blanked as a substantially linear iron core.

This linear iron core comprises a plurality of magnetic pole pieceswhich are interconnected into a linear configuration by interconnectingportions, each magnetic pole piece comprising a yoke portion, and atooth portion.

A plurality of such iron cores are stacked and laminated together, andthereafter windings are wound around the stacks of tooth portions,respectively, and the interconnecting portions are bent so as to formthe laminated iron core assembly into an annular shape, therebyproducing a core (stator) of a motor (see, for example, JP-A-11-156455).

For producing the above substantially-linear iron core, there isconventionally used an iron core-producing apparatus which comprisesguide means for guiding the strip linearly in one direction, a punch forblanking an iron core from the strip, and a die located beneath thepunch.

In such a conventional producing apparatus, when the strip is guidedonto the die by the guide means, the punch is driven into the die,thereby blanking an iron core from the strip.

In this conventional producing apparatus, the punch and the die aredisposed such that their longitudinal direction is parallel to thedirection of the width of the strip. Therefore, in the blanking step,the iron core is blanked from the strip in such a manner that thelongitudinal direction of the iron core is disposed parallel to thedirection of the width of the strip (see, for example, JP-A-11-156455).

In the production of the conventional iron core, the iron core isblanked, with its longitudinal direction disposed parallel to thedirection of the width of the strip, and therefore in order to increasethe overall length of the iron core, it has been necessary to increasethe width of the strip.

And besides, in the conventional iron core-producing apparatus, thepunch and the die are disposed in such a manner that their longitudinaldirection is parallel to the direction of the width of the strip asdescribed above. Therefore, when the width of the strip is increased inorder to increase the overall length of the iron core, a stripconveyance width of the guide means must be increased in accordance withthe increased width of the strip; otherwise, the iron core cannot beconveyed, and therefore can not be produced. In addition, unless alongitudinal width of a blanking drop hole, formed in the die, isincreased according to the width of the strip, the iron core can not beproduced from the strip by blanking.

In order to thus increase the overall length of the iron core, therehave been encountered problems that the width of the strip must beincreased and that the whole of the iron core-producing apparatusbecomes large in size.

When the whole of the iron core-producing apparatus becomes large insize, it is required to use a pressing device of a large size, which hasbeen very disadvantageous.

SUMMARY OF THE INVENTION

In view of the above circumstances, it is an object of this invention toprovide an iron core-producing method and an iron core-producingapparatus which are capable of producing an iron core of a large overalllength without the need for increasing a width of a strip and withoutthe use of an iron core-producing apparatus of a large size.

The above object has been achieved by an iron core-producing method ofthe invention for blanking a substantially linear iron core from astrip, comprising at least the step of blanking the iron core from thestrip in such a manner that a longitudinal direction of the iron core isinclined relative to a direction of a width of the strip.

An iron core-producing apparatus of the invention for blanking asubstantially linear iron core from a strip, comprises at least a punchdisposed such that its longitudinal direction is inclined relative to adirection of a width of the strip, and a die which is provided beneaththe punch, and is disposed such that its longitudinal direction isinclined relative to the direction of the width of the strip.

The iron core-producing method of the invention comprises at least thestep of blanking the iron core from the strip in such a manner that thelongitudinal direction of the substantially linear iron core is inclinedrelative to the direction of the width of the strip. Therefore, the ironcore, having an overall length larger than the width of the strip, canbe produced without the need for increasing the width of the strip. Andbesides, when producing this iron core, it is not necessary to use alarge-size producing apparatus since the width of the strip is notincreased.

The iron core-producing apparatus of the invention is designed to blankthe substantially linear iron core from the strip, and comprises atleast the punch disposed such that its longitudinal direction isinclined relative to the direction of the width of the strip, and thedie which is provided beneath the punch, and is disposed such that itslongitudinal direction is inclined relative to the direction of thewidth of the strip. Therefore, the iron core, having an overall lengthlarger than the width of the strip, can be produced without the need forincreasing the width of the strip. And besides, when producing this ironcore, it is not necessary to use a large-size producing apparatus sincethe width of the strip is not increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual top plan view of an iron core-producing apparatusof the present invention.

FIG. 2 is a conceptual top plan view of a strip W used in the producingapparatus of FIG. 1.

FIG. 3 is a conceptual top plan view of an iron core T produced atStation S2 of the producing apparatus of FIG. 1.

FIG. 4 is a conceptual top plan view showing the strip W in which aplurality of caulking portions L1 and a plurality of caulking portionsL2 are formed by stamping at Station S1 of the producing apparatus ofFIG. 1.

FIG. 5 is a conceptual top plan view of the strip W from which the ironcore T has been blanked from the strip W at Station S2 of the producingapparatus.

FIG. 6 is a conceptual top plan view of the strip W, showing a conditionin which caulking portions L1 and caulking portions L2 have been formedby stamping in the strip W of FIG. 5 at Station S3.

FIG. 7 is a conceptual top plan view of an iron core T produced atStation S4 of the producing apparatus of FIG. 1.

FIG. 8 is a conceptual top plan view of the strip W of FIG. 6 from whichthe iron core T of FIG. 7 has been blanked.

FIG. 9 is a conceptual top plan view of the strip W to which the processof Stations S1 to S4 has been repeatedly applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One preferred embodiment of the present invention will now be describedin detail with reference to the drawings.

FIG. 1 is a conceptual top plan view of an iron core-producing apparatus(hereinafter referred to merely as “producing apparatus”) of theinvention. FIG. 2 is a conceptual top plan view of a strip W used in theproducing apparatus of FIG. 1. FIG. 3 is a conceptual top plan view ofan iron core T produced at Station S2 (described later) of the producingapparatus of FIG. 1.

The iron core-producing apparatus 1 of FIG. 1 forms the substantiallylinear iron core T of FIG. 3 from the strip of W of FIG. 2 by blanking.

As shown in FIG. 3, the iron core T thus blanked from the strip W has alongitudinal extent, indicated by the dimension Y, and includes aplurality of magnetic pole pieces each having a discrete “T” shapeinterconnected by interconnecting portions Tc, each of the magnetic polepieces comprising a yoke portion Ta, and a tooth portion Tb formed onand projecting from the yoke portion Ta. The interconnected pole piecescollectively extend along a line that is inclined relative to the width(W) of the strip. Each tooth portion Tb and yoke portion Ta projectingtherefrom cooperatively define the discrete “T” shape. The discrete “T”shapes are interconnected through the portions Tc. The yoke portions Taare connected to each other to define a straight length with a widththat is locally reduced at the interconnection portions.

The iron cores T are sequentially stacked one upon another and boundtogether by caulking in such a manner that caulking portions, formed inthe magnetic pole pieces of each iron core T, are fitted respectively inthe caulking portions of the preceding iron core T in the step ofblanking the iron core T. Windings are wound respectively around thestacks of tooth portions Tb of the multiplicity of laminated iron coresT, and the interconnecting portions Tc each has a width less than awidth of a yoke portion Ta at a location where the interconnectingportion Tc and yoke portion Ta are joined to allow the iron cores T tobe bent at the interconnecting portions Tc so as to form the laminatediron cores T into an annular shape, thereby producing a core of a motor.

The producing apparatus 1 of FIG. 1 is provided with guidemeans/structure M for guiding the strip W in a predetermined manner in alongitudinal direction thereof.

This guide means includes engagement projections (not shown) forengagement in pilot holes P formed at a predetermined pitch in oppositeside edge portions (spaced from each other in the direction of thewidth) of the strip W (FIG. 2). A leading end portion of the strip W istaken up through the engagement of the engagement projections in thepilot holes P, so that the strip W is guided sequentially to Stations S1to S4.

The strip W is sequentially processed at Stations S1 to S4.

At Station S1, the caulking portions L1 and the caulking portions L2(FIG. 4) are formed in the strip W.

Caulking portion-forming holes 11 for simultaneously forming thecaulking portions L1 and the caulking portions L2 in the iron core T areprovided at Station S1. A longitudinal direction of rows of caulkingportion-forming holes 11 is inclined at an angle A (described later)relative to the direction X of the width of the strip W.

At Station S2, the iron core T (serving as a product) is formed from thestrip W by blanking.

A die 13 and a die holder 14 for fixing the die 13 are provided atStation S2.

A blanking drop hole 13 a is formed in the die 13, and extends in alongitudinal direction thereof. A longitudinal direction of the blankingdrop hole 13 a is inclined at the angle A relative to the widthwisedirection X of the strip W.

A product take-out device 21 is provided below the blanking drop hole 13a. This product take-out device 21 comprises a conveyor belt (not shown)whose longitudinal direction is inclined relative to the widthwisedirection of the strip W.

At Station S2, the iron core T is blanked in such a manner that thetooth portions Tb of the iron core T are disposed at lower sides of therespective yoke portions Ta as shown in FIG. 3.

At Station S3 of FIG. 1, caulking portions L1 and caulking portions L2(as shown in FIG. 6) are formed in the strip W (from which the iron coreT has been blanked at Stations S1 and S2) in order to produce another(fresh) iron core T.

Caulking portion-forming holes 16 for simultaneously forming thecaulking portions L1 and the caulking portions L2 are provided at thisStation S3. A longitudinal direction of rows of caulking portion-formingholes 16 is inclined at the angle A relative to the widthwise directionX of the strip W.

The caulking portions L1 and L2, which are identical in configuration tothe caulking portions L1 and L2 formed at Station S1, are formed bystamping at this Station S3. However, as shown in FIG. 6, the positionsof the caulking portions L1 and L2 (formed at Station S3) relative toeach other are reversed (inverted) with respect to the caulking portionsL1 and L2 formed at Station S1.

At Stations S4 of FIG. 1, the fresh iron core T (serving as a product)is blanked from the strip W in which the caulking portions L1 and L2have been formed at Station S3.

A die 18 and a die holder 19 for fixing the die 18 are provided at thisStation S4.

A blanking drop hole 18A is formed in the die 18, and extends in alongitudinal direction thereof. A longitudinal direction of the blankingdrop hole 18 a is inclined at the angle A relative to the widthwisedirection X of the Strip W.

The iron core T, formed by blanking at Station S4, is identical inconfiguration, including length, to the iron core T formed by blankingat Station S2. However, at Station S4, the iron core T is blanked insuch a manner that the tooth portions Tb of this iron core T aredisposed at upper sides of the respective yoke portions Ta as shown inFIG. 7 (described later).

The process of producing the iron cores T from the strip W by the use ofthe above producing apparatus 1 will be described below in detail withreference to FIGS. 1 to 9.

At Station S1 of FIG. 1, when the strip W of FIG. 2 is guided by theguide means to a position above the caulking portion-forming holes 11, apunch (not shown) intrudes into the caulking portion-forming holes 11 tosimultaneously form the plurality of caulking portions L1 and theplurality of caulking portions L2 (FIG. 3) at a predetermined pitch asshown in FIG. 4.

FIG. 4 is a conceptual top plan view showing the strip W in which theplurality of caulking portions L1 and the plurality of caulking portionsL2 are thus formed.

The caulking portions L1 as well as the caulking portions L2, formed inthe strip W, correspond in number to the magnetic pole pieces of theiron core T (FIG. 3).

The row of caulking portions L1 as well as the row of caulking portionsL2, are formed to be disposed in a direction inclined at the angle A(≠90°) relative to the widthwise direction of the strip W. It will beappreciated also from the arrangement of the thus formed caulkingportions L1 and L2 that the longitudinal direction of the rows ofcaulking portion-forming holes 11, as well as the longitudinal directionof the punch for intruding into these holes 11, is inclined at the angleA (≠90°) relative to the widthwise direction of the strip W.

At Station S1, thus, the caulking portion-forming holes 11 and the punchfor intruding into these holes 11 are so arranged that the longitudinaldirection of the rows of caulking portion-forming holes 11, as well asthe longitudinal direction of the punch for intruding into these holes11, is inclined at the angle A (≠90°) relative to the widthwisedirection of the strip W. Therefore, a longitudinal width M (see FIG. 4)of the rows of caulking portion-forming holes 11, as well as alongitudinal width M (see FIG. 4) of the punch for intruding into theseholes 11, can be made larger than the width X of the strip W. Therefore,a distance M between the two caulking portions L1 disposed respectivelyat the opposite ends of the row of caulking portions L1, as well as adistance M between the two caulking portions L2 disposed respectively atthe opposite ends of the row of caulking portions L2, can be made largerthan the width X of the strip W (M>X) as shown in FIG. 4.

Then, at Station S2 of FIG. 1, when the strip W is conveyed to aposition above the blanking drop hole 13 a in the die 13, a punch (notshown) intrudes into the blanking drop hole 13 a to blank the iron coreT of FIG. 3 from the strip W of FIG. 4. FIG. 5 is a conceptual top planview of the strip W from which the iron core T of FIG. 3 has beenblanked.

As shown in FIG. 3, the caulking portion L1 and the caulking portion L2have been formed in each of the magnetic pole portions of the thusblanked iron core T.

On the other hand, a blanked-out hole C is formed in the strip W as aresult of blanking of the iron core T as shown in FIG. 5. A longitudinaldirection of the thus formed blanked-out hole C is inclined at the angleA (≠90°) relative to the widthwise direction of the strip W. It will beappreciated also from the manner of formation of this blanked-out hole Cthat the longitudinal direction of the blanking drop hole 13 a, as wellas the longitudinal direction of the punch for intruding into this hole13 a, is inclined at the angle A (≠90°) relative to the widthwisedirection of the strip W.

At this Station S2, thus, the blanking drop hole 13 a and the punch forintruding into this hole 13 a are so arranged that the longitudinaldirection of the blanking drop hole 13 a, as well as the longitudinaldirection of the punch for intruding into this hole 13 a, is inclined atthe angle A (≠90°) relative to the widthwise direction of the strip W.Therefore, a longitudinal width Y of the blanking drop hole 13 a, aswell as a longitudinal width Y of the punch for intruding into this hole13 a, can be made larger than the width X of the strip W (Y>X).Therefore, the overall length Y (see FIG. 3) of the blanked iron core Tcan be made larger than the width X of the strip W (Y>X).

At Station S3 of FIG. 1, when the strip W of FIG. 5 is guided by theguide means to a position above the caulking portion-forming holes 16, apunch (not shown) intrudes into the caulking portion-forming holes 16 tosimultaneously form the caulking portions L1 and the caulking portionsL2 as shown in FIG. 6.

FIG. 6 is a conceptual top plan view of the strip W, showing a conditionin which the caulking portions L1 and the caulking portions L2 have beenformed by stamping in the strip W of FIG. 5 at Station S3.

The caulking portions L1 as well as the caulking portions L2, formed inthe strip W, correspond in number to the magnetic pole pieces of theiron core T (FIG. 7).

The row of caulking portions L1 as well as the row of caulking portionsL2, are formed to be disposed in a direction inclined at the angle A(≠90°) relative to the widthwise direction of the strip w. It will beappreciated also from the arrangement of the thus formed caulkingportions L1 and L2 that the longitudinal direction of the rows ofcaulking portion-forming holes 16, as well as the longitudinal directionof the punch for intruding into these holes 16, is inclined at the angleA (≠90°) relative to the widthwise direction of the strip W.

At Station S3, thus, the caulking portion-forming holes 16 and the punchfor intruding into these holes 16 are so arranged that the longitudinaldirection of the rows of caulking portion-forming holes 16, as well asthe longitudinal direction of the punch for intruding into these holes16, is inclined at the angle A (≠90°) relative to the widthwisedirection of the strip W. Therefore, a longitudinal width M (see FIG. 4)of the rows of caulking portion-forming holes 16, as well as alongitudinal width M of the punch for intruding into these holes 16, canbe made larger than the width X of the strip W. Therefore, a distance M(see FIG. 4) between the two caulking portions L1 disposed respectivelyat the opposite ends of the row of caulking portions L1, as well as adistance M (see FIG. 4) between the two caulking portions L2 disposedrespectively at the opposite ends of the row of caulking portions L2,can be made larger than the width X of the strip W (M>X).

Then, at Station S4 of FIG. 1, when the strip W of FIG. 6 is conveyed toa position above the blanking drop hole 18 a in the die 18, a punch (notshown) intrudes into the blanking drop hole 18 a to blank the iron coreT from the strip W of FIG. 6 as shown in FIG. 7. FIG. 7 is a conceptualtop plan view of the iron core T formed at this Station S4. FIG. 8 is aconceptual top plan view of the strip W from which the iron core T ofFIG. 7 has been blanked.

As shown in FIG. 7, the caulking portion L1 and the caulking portion L2have been formed in each of the magnetic pole portions of the thusblanked iron core T.

A blanked-out hole C is formed in the strip W as a result of blanking ofthe iron core T as shown in FIG. 8. A longitudinal direction of the thusformed blanked-out hole C is inclined at the angle A (≠90°) relative tothe widthwise direction of the strip W. It will be appreciated also fromthe manner of formation of this blanked-out hole C that the longitudinaldirection of the blanking drop hole 18 a, as well as the longitudinaldirection of the punch for intruding into this hole 18 a, is inclined atthe angle A (≠90°) relative to the widthwise direction of the strip W.

At this Station S4, thus, the blanking drop hole 18 a and the punch forintruding into this hole 18 a are so arranged that the longitudinaldirection of the blanking drop hole 18A, as well as the longitudinaldirection of the punch for intruding into this hole 18 a, is inclined atthe angle A (≠90°) relative to the widthwise direction of the strip W.Therefore, a longitudinal width Y of the blanking drop hole 18 a, aswell as a longitudinal width Y of the punch for intruding into this hole18 a, can be made larger than the width X of the strip W (Y>X).Therefore, the overall length Y (see FIG. 3) of the blanked iron core T(FIG. 7) can be made larger than the width X of the strip (Y>X).

Two iron cores T of equal length can be produced by effecting theprocess of Stations S1 to S4. In this producing apparatus 1, a pluralityof iron cores (two per process) can be produced from the strip W byrepeating the process of Stations S1 to S4. At each of Stations S1 andS3, the

caulking portions L1 and L2 are formed in the iron core T, and throughholes are formed as the respective caulking portions L1 and L2 throughthe first (lowermost-layer) iron core T, while in each of the other ironcores T (that is, the second to uppermost-layer iron Cores T), the typeof caulking portions (each of which assumes a caulking recess whenviewed from one side of the iron core, and also assumes a caulkingprojection when viewed from the other side thereof) are formed as therespective caulking portions L1 and L2. At each of Stations S2 and S4,the iron core T is blanked from the strip, and moves through theblanking drop hole 13 a, 18 a into a position beneath the blanking drophole 13 a, 18 a. At Station S4 at which an iron core T is first blanked,the iron core T, blanked at this time, is placed on theprecedingly-produced iron core T, with its caulking projections fittedrespectively in the through holes in the precedingly-produced iron coreT, and the two iron cores T are laminated (stacked) and bound togetherby caulking. Thereafter, at each of Stations S2 and S4, a fresh ironcore T is blanked, and is placed on the precedingly-stacked iron core T,with its caulking projections fitted respectively in the caulkingrecesses in this precedingly-stacked iron core T, and the fresh ironcore T is laminated and joined onto the precedingly-stacked iron core Tby caulking. This process is repeatedly carried out, so that thepredetermined number of iron cores T are blanked, and are laminated andbound together by caulking.

FIG. 9 is a conceptual top plan view of the strip W to which the processof Stations S1 to S4 has been repeatedly applied. As shown in FIG. 9, aplurality of rows of blanked-out holes C are formed in the strip W inparallel relation to one another.

The predetermined number of iron cores T, blanked and laminated bycaulking at Station S2, are located on the product take-out device 21,and are discharged to the exterior of the producing apparatus 1 by theconveyor belt of the product take-out device 21.

The predetermined number of iron cores T, blanked and laminated togetherby caulking at Station S4, are located on the product take-out device22, and are discharged to the exterior of the producing apparatus 1 bythe conveyor belt of the product take-out device 22.

As described above, the method of the invention for producing the ironcore T includes at least the step of blanking the substantially lineariron core T from the strip W in such a manner that the longitudinaldirection of the iron core T is inclined relative to the widthwisedirection of the strip W. Therefore, the iron core T, having the overalllength Y larger than the width X of the strip W, can be produced, usingthe strip W having the conventional width X, that is, without the needfor increasing the width X of the strip W.

In the case of increasing the overall length Y of the iron core T, thewidth X of the strip W does not need to be increased, and therefore itis not necessary that a strip guide width of the guide means should beincreased in accordance with the width X of the strip W as in theconventional method, and also it is not necessary that the longitudinalwidth of the blanking drop holes 13 a and 18 a should be increased as inthe conventional method.

Namely, when producing the iron core T having the large overall length,it is not necessary to increase the width W of the strip W, andtherefore it is not necessary to use a large-size producing apparatusincluding the guide means with a large strip conveyance width, and theblanking drop holes with a large width.

This producing method can further includes the step of changing theangle A of inclination of each of the dies 13 and 18 and the angle A ofeach of the punches (for intruding respectively into the dies 13 and 18)in accordance with the overall length Y of iron cores to be produced,and by doing so, various iron cores of different overall lengths can beproduced.

The producing apparatus 1 of the invention includes at least the puncheseach of which is provided for blanking the substantially linear ironcore T from the strip W, and is disposed such that its longitudinaldirection is inclined relative to the widthwise direction of the strip Was described above, and the dies 13 and 18 which are providedrespectively beneath these punches, and are disposed such that theirlongitudinal directions are inclined relative to the widthwise directionof the strip W as described above. Therefore, the iron core T, havingthe overall length Y larger than the width X of the strip W, can beproduced, using the strip W having the conventional width X, that is,without the need for increasing the width X of the strip W.

When increasing the overall length Y of the iron core, it is notnecessary to increase the width W of the strip W, and therefore it isnot necessary to use a large-size producing apparatus including theguide means with a large strip guide width, and the blanking drop holes13 a and 18 a with a large longitudinal width as in the conventionalapparatus.

Namely, when producing the iron core T with the large overall length,the width of the strip W does not need to be increased, and therefore itis not necessary to use such a large-size producing apparatus.

According to the present invention, the angle A of the inclination isset in a range from 20° to 70°, preferably in a range from 40° to 60°.Because the length Y of the iron core T can be represented by Y=X/cos A,it is understandable that the length Y is lengthened 1.1× to 2.9×,preferably 1.3× to 2.0×.

This producing apparatus 1 can further includes means for changing theangle A of inclination of each of the blanking drop holes 13 a and 18 aand the angle A of each of the punches (for intruding respectively intothe blanking drop holes 13 a and 18 a) in accordance with the overalllength Y of iron cores T to be produced, and by doing so, various ironcores of different overall lengths can be produced.

Although the producing apparatus 1 of the above embodiment includesStations S1 and S2 for producing one iron core T, and Stations S3 and S4for producing another iron core T, this producing apparatus of theinvention may include at least Stations S1 and S2 or Stations S3 and S4for producing one iron core T.

Although the producing method of the invention produces a plurality ofiron cores T, the invention can be applied to a method of producing oneiron core T.

Although the above embodiment illustrates the iron core T of the windingcore-type, the producing method and apparatus of the invention can beeffectively applied to the cases where iron cores of various shapes areformed by blanking.

As described above, the iron core-producing apparatus of the inventionis effectively used as a producing apparatus for producing an iron coreserving as a part of a motor core and particularly for producing an ironcore with a large overall length, and the iron core-producing method iseffectively used as a method of producing this iron core.

What is claimed is:
 1. An iron-core producing method that blanks ironcores from an iron strip by guiding the iron strip sequentially throughan iron core-producing apparatus having a plurality of workstations, themethod comprising: guiding, by a guide, the iron strip to a firstworkstation having a punch that intrudes into caulking portion-formingholes; simultaneously forming, by the first workstation, first pluralsets of caulking portions at a predetermined pitch in the iron strip;guiding the iron strip from the first workstation to a secondworkstation within the iron-core producing apparatus; and forming, bythe second workstation, a first iron core from the iron strip byblanking, such that tooth portions of the first iron core are disposedat lower sides of respective yoke portions.
 2. The iron-core producingmethod of claim 1, the method further comprising: providing engagementprojections in the guide that engage pilot holes formed at apredetermined pitch in opposite side edge portions of the iron strip. 3.The iron-core producing method of claim 1, the method furthercomprising: inclining a longitudinal direction of rows of the caulkingportion-forming holes in the first workstation at an angle relative tothe direction of the width of the iron strip.
 4. The iron-core producingmethod of claim 1, the method further comprising: providing a die and adie holder that fixes the die at the second workstation; and forming ablanking drop hole in the die at the second workstation that extends ina longitudinal direction and is inclined at the angle relative to thedirection of the width of the iron strip.
 5. The iron-core producingmethod of claim 1, the method further comprises: providing, at thesecond workstation, a product take-out device below the blanking drophole, the product take-out device including a conveyor belt whoselongitudinal direction is inclined relative to the direction of thewidth of the iron strip.
 6. The iron-core producing method of claim 1,the method further comprising: providing a third workstation; guidingthe iron strip from the second workstation to a third workstation;providing, at the third workstation, a punch that intrudes into caulkingportion-forming holes and that simultaneously forms second plural setsof caulking portions in the iron strip at the predetermined pitch in theiron strip; providing a fourth workstation; guiding the iron strip fromthe third workstation to a fourth workstation; and forming, at thefourth workstation, a second iron core by blanking from the iron stripin which the second plural sets of caulking portions were formed at thethird workstation.
 7. The iron-core producing method of claim 6, themethod further comprising: including a longitudinal direction of rows ofthe caulking portion-forming holes in the third workstation at an anglerelative to the direction of the width of the iron strip.
 8. Theiron-core producing method of claim 7, the method further comprising:reversing positions of the second plural sets of caulking portionsformed at the third workstation relative to each other in an invertedconfiguration with respect to the first plural sets of caulking portionsformed at the first workstation.
 9. The iron-core producing method ofclaim 6, the method further comprising: providing a die and a die holderthat fixes the die at the fourth workstation.
 10. The iron-coreproducing method of claim 9, the method further comprising: forming, atthe fourth workstation, a blanking drop hole in the die that extends ina longitudinal direction and is inclined at the angle relative to thedirection of the width of the iron strip.
 11. The iron-core producingmethod of claim 10, the method further comprising: providing, at thefourth workstation, a product take-out device below the blanking drophole, the product take-out device including a conveyor belt whoselongitudinal direction is inclined relative to the direction of thewidth of the iron strip.
 12. The iron-core producing method of claim 6,the method further comprising: forming the second iron core, formed byblanking at the fourth workstation, identical in configuration to thefirst iron core formed by blanking at the second station, except theiron core formed at the fourth workstation is blanked in such a mannerthat tooth portions of the second iron core are disposed at upper sidesof the respective yoke portions.
 13. The iron-core producing method ofclaim 1, the method further comprising: inclining the longitudinaldirection of the iron core at an acute angle relative to a direction ofa width of the iron strip.
 14. The iron-core producing method of claim1, the method further comprising: forming the first iron core and thesecond iron core such that the first iron core and the second iron coreeach comprise a plurality of discrete, magnetic pole pieces joined byinterconnecting portions that are bendable to form an annular shape. 15.The iron-core producing method of claim 14, further comprising: formingeach magnetic pole piece such that each magnetic pole piece comprises ayoke portion and a tooth portion formed on and projecting from the yokeportion.
 16. The iron-core producing method of claim 15, the methodfurther comprising: forming the interconnecting portions such that theinterconnecting portions have a width less than a width of yoke portionsat locations where the interconnecting portions and yoke portions arejoined to allow the first iron core and the second iron core to be bentinto the annular shape.
 17. The iron-core producing method of claim 13,the method further comprising: producing the first iron core and thesecond iron core from the iron strip such that the first iron core andthe second iron core have lengths that are greater than the width of theiron strip.
 18. The iron-core producing method of claim 17, the methodfurther comprising: providing a selector such that the acute angle isselectable to produce a plurality of iron cores of different lengths.19. The iron-core producing method of claim 1, the method furthercomprising: inclining the longitudinal direction of the iron core in arange from 20 degrees to 70 degrees relative to a direction of a widthof the iron strip.
 20. The iron-core producing method of claim 1, themethod further comprising: inclining the longitudinal direction of theiron core in a range from 40 degrees to 60 degrees relative to adirection of a width of the iron strip.